# CVE-2025-38685: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit

> A local attacker can trigger an out-of-bounds write in the Linux kernel's fbdev subsystem via a specific ioctl, potentially leading to code execution or privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-66794, AZL-73836, BELL-CVE-2025-38685, DEBIAN-CVE-2025-38685, GHSA-qq5r-fpg9-2mj7, ROOT-OS-DEBIAN-11-CVE-2025-38685, ROOT-OS-DEBIAN-12-CVE-2025-38685, ROOT-OS-UBUNTU-2204-CVE-2025-38685, ROOT-OS-UBUNTU-2404-CVE-2025-38685, UBUNTU-CVE-2025-38685

## What is CVE-2025-38685?

CVE-2025-38685 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 4 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

fbdev: Fix vmalloc out-of-bounds write in fast_imageblit

This issue triggers when a userspace program does an ioctl
FBIOPUT_CON2FBMAP by passing console number and frame buffer number.
Ideally this maps console to frame buffer and updates the screen if
console is visible.

As part of mapping it has to do resize of console according to frame
buffer info. if this resize fails and returns from vc_do_resize() and
continues further. At this point console and new frame buffer are mapped
and sets display vars. Despite failure still it continue to proceed
updating the screen at later stages where vc_data is related to previous
frame buffer and frame buffer info and display vars are mapped to new
frame buffer and eventully leading to out-of-bounds write in
fast_imageblit(). This bheviour is excepted only when fg_console is
equal to requested console which is a visible console and updates screen
with invalid struct references in fbcon_putcs().

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2025-38685?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38685?

Apply the vendor's patch.

## Is CVE-2025-38685 being exploited?

There is no known exploitation of CVE-2025-38685 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38685 and fix it if it is affected.

What it is: CVE-2025-38685 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 4 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-38685 in the wild and no public exploit code.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-38685/ (Markdown: https://insights.sbomify.com/CVE-2025-38685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38685
- OSV: https://osv.dev/vulnerability/CVE-2025-38685

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38685/
Summaries are generated and may contain mistakes; the official description above is the record.